Rotary actuating drive and rotary switch

ABSTRACT

To simplify the design of a rotary actuator, in particular for an “R”-type waveguide switch, having a permanently magnetized rotor and a plurality of stator windings surrounding the rotor in a rim-like fashion, for generating magnetic fields which place the rotor in one of a first plurality of positions, it is proposed to finish the actuator with elements for exerting a corrective torque on the rotor, the elements placing the rotor, in the currentless state of the stator windings, in a target position of a second plurality of positions, each position of the first plurality having assigned to it a target position.

FIELD OF THE INVENTION

The present invention relates to a rotary actuator having a permanentlymagnetized rotor and a plurality of stator windings surrounding therotor in a rim-like fashion, for generating magnetic fields that placethe rotor in one of a first plurality of positions.

BACKGROUND INFORMATION

Rotary actuators can be used as the drive for rotary switches, forexample, an “R”-type waveguide switch in satellite technology.

Currently, stepping motors are generally used as actuators for purposesof this type, such as are described in European Patent No. 0 635 929.However, stepping motors have a number of characteristics that make themnot seem optimally suited as actuators for rotary switches. Steppingmotors are generally designed to generate a large torque that isdistributed as uniformly as possible in the course of one rotation ofthe motor shaft, the torque making it possible to smoothly drive amechanism that is braked using friction. This requires a minutestaggering of the stator windings in the circumferential directionaround the rotor, necessitating a multiplicity of terminal connectionsthat are cumbersome to connect to wires. FIG. 5a depicts an example of arim-like arrangement of stator windings, which can place an (undepicted)rotor in four positions, each offset by 45° with respect to the others.Stator windings 1 through 4 are divided here into two diametricallyopposite segments 1 a, 1 b, . . . 4 a, 4 b. The total of eight segmentsare mounted on a ring core 5, which lies in the plane of the Figure andperpendicular to rotational axis 6 of an (undepicted) rotor. FIG. 5bdepicts the alignments of magnetic fields B₁ . . . B₄, which areobtained by sending current through segment pairs 1 a, 1 b . . . 4 a, 4b. These vectors indicate the position in which the rotor is placed inthe interior space of ring core 5. Each neighboring vector has anangular distance from adjacent vectors of 45°. By sending currentthrough the winding segments having the opposite sign, vectors can alsobe generated in the opposite direction, but they generally have nopractical significance in applications of the rotary actuator forsetting a rotary switch.

The large number of necessary segments makes it difficult to achieve acompact design of the actuator and renders its manufacturetime-consuming and expensive.

From Japanese Laid-Open Patent Application No. 10 178 770, and therelated English abstract published in Patent Abstracts of Japan, Volume1998, No. 11, Sep. 30, 1998, a motor, in particular a stepping motor, isknown which has a controllable stop position. This motor has apermanently magnetized rotor and a plurality of stator windingssurrounding the rotor in a rim-like fashion, for generating magneticfields for the purpose of placing the rotor in a plurality of positions.To place the rotor in specific positions, permanent magnets are providedbetween the stator windings.

SUMMARY OF THE INVENTION

According to the present invention, in a rotary actuator of the typecited above, elements are provided for exerting a corrective torque onthe rotor, the elements, in the currentless state of the statorwindings, placing the rotor in a target position from a second pluralityof positions, a target position being assigned to each position of thefirst plurality. Therefore, whereas in conventional rotary actuators thestator windings themselves must place the rotor in a target position, inthe actuator according to the present invention, this task is taken onby the elements for exerting a corrective torque. Therefore, there nolonger exists the requirement that the stator windings must have anarrangement having double symmetry in order to be able to set ndifferent positions in an angular range of 180°. Their arrangement cantherefore be simpler, a high degree of symmetry in any case in theelements for exerting the corrective torque. But since the latter issmaller than the torque to be exerted by the stator windings and sincethe range of the latter can be significantly smaller, it is possiblethat the elements for exerting the corrective torque can also besignificantly smaller and more compact.

In particular, these elements can be permanent magnets and therefore donot need to be wired. Thus according to the present invention, it ispossible to arrange the stator windings about the rotor in an unpairedfashion, which cuts in half the number of contacts that are needed forthe power supply of the stator windings, and that must be soldered orconnected in some other way. The possibility of using a number of statorwindings that is smaller than the number of the first positions makespossible a further simplification of the design.

According to one preferred embodiment, the rotary actuator has fourfirst positions and three stator windings.

Further features of the rotary actuator according to the presentinvention and of a rotary switch that is equipped with an actuator ofthis type can be derived from the description of the exemplaryembodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a schematically depicts an exemplary embodiment of a rotaryactuator according to the present invention having three stator windingsand four first positions.

FIG. 1b depicts the vectors that correspond to the magnetic fieldsgenerated only by the stator windings and to the target positions of therotary actuator.

FIG. 2 depicts a second exemplary embodiment of a rim-like arrangementof stator windings of a rotary actuator according to the presentinvention.

FIG. 3 depicts a network having four inputs and three outputs forsupplying the stator windings with current corresponding to the fourfirst positions.

FIG. 4 schematically depicts an “R”-type waveguide switch in fourdifferent switching positions.

FIG. 5a depicts a conventional arrangement of stator windings; and

FIG. 5b depicts the orientation of the magnetic fields generated by thestator windings in FIG. 5a.

DETAILED DESCRIPTION

FIG. 1a depicts the components of a rotary actuator according to thepresent invention. The actuator includes three stator windings 1, 2, 3,which are arranged in a rim-like fashion, symmetrically about an axis 6that is perpendicular to the plane of the Figure, at an angular distancein each case of 120°. The stator windings can be selectively connectedto an (undepicted) power supply, the polarity of power supply terminals8 of the stator windings being selected so that windings 1 and 3generate a magnetic field that is equally oriented with respect to animaginary circumferential line 9, and stator winding 2 generates amagnetic field having the opposite orientation. Thus as a result of acurrent being sent through stator windings 1, 2, 3, magnetic fields B₁,B₂, B₃, having the orientations depicted in FIG. 1b, are obtained, whichare offset by 60° with respect to each other.

A rotor 7, which for the sake of simplicity is depicted in FIG. 1a as abar magnet, can rotate freely about axis 6 under the influence of themagnetic fields generated by stator windings 1, 2, 3; in FIG. 1a, it isdepicted in the position which corresponds to the case in which onlystator winding 1 is supplied with current.

Rotor 7 can adopt other positions corresponding to the orientation ofmagnetic fields B₂, B₃, if one of windings 2, 3 is supplied withcurrent.

Four auxiliary magnets 11, 12, 13, 14 are mounted so as to be radiallyoriented at different locations outside the area covered by rotor 7 inits rotary motion. A first auxiliary magnet 11 is mounted in a positionwhich shifts the orientation of magnetic field B₁ by 7.5° in theclockwise direction. Auxiliary magnet 11 has a polarity such that itexerts an attractive force on rotor 7 in the position depicted in FIG.1a adopted under the influence of magnetic field B₁. If the power supplyto winding 1 is terminated, rotor 7 under the influence of auxiliarymagnet 11 rotates to a target position Z₁ (see FIG. 1b), in which it isdirectly facing auxiliary magnet 11.

A further auxiliary magnet 14 is arranged so as to be offset withrespect to auxiliary magnet 11 by 45° in the clockwise direction and tohave a polarity that is opposite to the latter's. Under the influence ofa magnetic field generated by winding 3, rotor 7 adopts a positioncorresponding to vector B₃ in FIG. 1b, if this magnetic field isswitched off, rotor 7 under the influence of auxiliary magnet 14 rotates7.5° to a target position, which corresponds to vector Z₄ in FIG. 1b.Vectors Z₁, Z₄ constitute an angle of 135°.

Two further auxiliary magnets 12, 13 are arranged so that they canmaintain rotor 7 in target positions Z₂, Z₃. Four target positions Z₁,Z₂, Z₃, Z₄ are offset by 45° with respect to each other.

Auxiliary magnets 11, 12, 13, 14 are dimensioned so that they have thecapacity to pull the rotor to themselves from an angular distance of upto roughly +/−20°.

Auxiliary magnets 11, 13, on the one hand, and 12, 14, on the otherhand, have different polarities with respect to the radial direction andcooperate with different poles of rotor 7. The influence of each of themcan be supported by an (undepicted in FIG. 1a) second auxiliary magnetsituated diametrically opposite. If the rotary actuator has four targetpositions, as in the case described here by way of example, there aretherefore eight locations at which auxiliary magnets can be arranged.However, it is sufficient if for every target position only one of thesetwo locations is occupied. Preferably, as is depicted in FIG. 1a, theone of the two locations is occupied which is left vacant by a statorwinding, because this makes the more compact design possible.

As can be seen in FIG. 1b, vector B₂ of the magnetic field generated bystator winding 2 lies precisely on the line bisecting the angle betweentwo target positions Z₃ and Z₂. Therefore, it is not possible to set twotarget positions Z₂ or Z₃, by one of the stator windings beingtemporarily charged with current and rotor 7 then being left to theinfluence of the auxiliary magnets, which pull it into the desiredtarget position. For this reason, three stator windings 1, 2, 3 areadvantageously provided with current via a network, as depicted in FIG.3. The network has four inputs 20 ₁ through 20 ₄ and three outputs 21 ₁through 21 ₃. Inputs 20 ₁ and 20 ₄ make it possible for a current toflow via a diode 22 ₁, or 22 ₃, to winding 1, or 3, respectively. If oneof these inputs is supplied with current, rotor 7 as a consequenceadopts a first position, which corresponds to the orientation of amagnetic field B₁, or B₃. If input 20 ₂ is supplied with current, onepart of the current flows via a diode 22 ₃ to winding 2 and the rest ofthe current flows via a diode 22 ₂ and a resistor 23 ₁ to winding 1. Themagnetic fields generated by windings 1, 2 overlap each other in a fieldB₂₁, whose vector is depicted in FIG. 1b by a dotted line. As aconsequence, if input 20 ₂ is supplied with current, rotor 7 adopts afirst position corresponding to field B₂₁, from which, if the powersupply is switched off, it can reliably be pulled into target positionZ₂ by corresponding auxiliary magnet 12.

If the choice of the resistance value of resistor 23 ₁ is suitable, theangular distance between B₂₁ and Z₂ can be made as small as desired, orthe two positions can be brought into agreement.

By analogy to input 20 ₂, input 20 ₃ is connected via diode 22 ₄ towinding 2 and via diode 22 ₅ and a resistor 23 ₃ to winding 3, so that acurrent that is applied to the network at input 20 ₃ is distributed overwindings 2, 3 and results in a superimposed magnetic field B₂₁, as isdepicted in FIG. 1b by a dotted line.

In this manner, by one of inputs 20 ₁ through 20 ₄ of the network inFIG. 3 being selectively charged with current, it is possible to placerotor 7 in one of a plurality of first positions and subsequently, underthe influence of auxiliary magnets 11 through 14, to cause it to pass toa target position, which can be offset with respect to the firstposition by a small angle.

Optionally, a resistor 23 ₃ can be arranged upstream of output 21 ₂ thatis assigned to winding 2, to make the resistance of the arrangement madeup of network and windings the same for all inputs 20 ₁ through 20 ₄ ofthe network.

One preferred application of the rotary actuator is the drive of an“R”-type switch 25, as depicted in FIG. 4 in different switchingpositions. This switch 25 has a frame having four input/outputs 26 ₁through 26 ₄ and an adjusting body 27 that rotates in the frame.Adjusting body 27 is coupled to the rotor of an actuator, as isdescribed with regard to FIG. 1 and FIG. 2, and can therefore beadjusted among four positions, which are depicted in parts a through dof FIG. 4.

Adjusting body 27 contains three channels 28, which in the variousswitching positions are connected in each case to differentinput/outputs 26 ₁ . . . 26 ₄. In three of the four switching positions,any input/output, for example 26 ₁, is connected in each case with oneof the three other outputs 26 ₂ through 26 ₄, and in a fourth switchingstate it is disconnected.

These “R”-type switches, especially “R”-type waveguide switches, inwhich the input/outputs and the channels are waveguide for highfrequency signals, are used especially in space travel for theredundancy switches in payloads.

It is obvious that the rotary actuator that is described abovespecifically for the case of three stator windings and four targetpositions can also be applied for other numbers of stator windings andpositions.

In addition, magnetic fields such as magnetic fields B₁, B₂ and B₃ inFIG. 1b, which define the first positions of the rotor, do notnecessarily have to be generated by one single stator winding. Thus, forexample, in the case of FIG. 2, if one of the stator windings, forexample winding 2, is supplied with a current in accordance with thesigns indicated at their terminals 8, it is conceivable, in order togenerate field B₂, to simultaneously supply current to stator windings 1and 3 in series with each other and parallel to winding 2, in accordancewith the signs indicated at terminals 8 of windings 1 and 3, so as, inthis manner, to strengthen the magnetic field in the interior space ofring core 5, to which rotor 7 is exposed.

What is claimed is:
 1. A rotary actuator, comprising: a permanentlymagnetized rotor; a plurality of stator windings surrounding thepermanently magnetized rotor in a rim-like fashion and for generating amagnetic field, the stator windings placing the permanently magnetizedrotor in one of a first plurality of positions, wherein the statorwindings are coplanar and arranged so as to be unpaired; an arrangementfor exerting a corrective torque on the permanently magnetized rotor,the arrangement for exerting the corrective torque, in a currentlessstate of the stator windings, placing the permanently magnetized rotorin a target position of a second plurality of positions, each positionof the first plurality of positions having assigned thereto acorresponding one of the second plurality of positions as the targetposition; and a network having n inputs and m outputs, n being a numberof the first plurality of positions and m being a number of the statorwindings, wherein: each one of the stator windings is connected to oneof the m outputs, and the network distributes to the stator windings acurrent applied at one of the n inputs in order to set one of the firstplurality of positions that is assigned to a respective one of the ninputs.
 2. The rotary actuator according to claim 1, wherein: thepermanently magnetized rotor includes a magnet that is aligned so as tobe perpendicular to a rotational axis.
 3. The rotary actuator accordingto claim 1, wherein: the stator windings are uniformly distributedaround a rotational axis in a circumferential direction.
 4. The rotaryactuator according to claim 1, further comprising: a ring coresurrounding the permanently magnetized rotor and on which the statorwindings are arranged.
 5. The rotary actuator according to claim 1,wherein: the number m of the stator windings is smaller than the numbern of the first plurality of positions.
 6. The rotary actuator accordingto claim 1, wherein: the arrangement for exerting the corrective torqueincludes a plurality of permanent magnets.
 7. The rotary actuatoraccording to claim 1, wherein: a resistance of all n inputs is the same.8. The rotary actuator according to claim 1, wherein: the statorwindings include three stator windings, and the plurality of firstpositions includes four first positions.
 9. The rotary actuatoraccording to claim 1, wherein: adjoining target positions have anangular distance of 45°.
 10. The rotary switch according to claim 1,wherein: the rotary switch is an “R”-type waveguide switch.
 11. Therotary actuator according to claim 1, wherein: the arrangement includesa plurality of elements that are arranged in an asymmetric manner abouta longitudinal axis of the rotary actuator.
 12. A rotary switch,comprising: a rotary actuator that includes: a permanently magnetizedrotor; a plurality of stator windings surrounding the permanentlymagnetized rotor in a rim-like fashion and for generating a magneticfield, the stator windings placing the permanently magnetized rotor inone of a first plurality of positions, wherein the stator windings arecoplanar and arranged so as to be unpaired; an arrangement for exertinga corrective torque on the permanently magnetized rotor, the arrangementfor exerting the corrective torque, in a currentless state of the statorwindings, placing the permanently magnetized rotor in a target positionof a second plurality of positions, each position of the first pluralityof positions having assigned thereto a corresponding one of the secondplurality of positions as the target position; and a network having ninputs and m outputs, n being a number of the first plurality ofpositions and m being a number of the stator windings, wherein: each oneof the stator windings is connected to one of the m outputs, and thenetwork distributes to the stator windings a current applied at one ofthe n inputs in order to set one of the first plurality of positionsthat is assigned to a respective one of the n inputs.